Fabrication of functional discarded shells-based superhydrophobic coatings

Abstract

With the expansion of shellfish aquaculture, there has been an increase in the number of discarded shells, leading to a range of issues, including environmental pollution, global warming, health risks, and the eutrophication of coastal waters. The recycling of discarded mussel shells holds great research significance. In this study, we present a method for preparing a functional shell powder-based superhydrophobic coating filler by modifying shell powder with Mg(OH)₂ and stearic acid (SA). Mg(OH)₂ crystals were utilized to modify shell powder and enhance the abrasion resistance of superhydrophobic coatings. Additionally, loading SA can decrease the free energy of the filler surface, thereby improving the hydrophobic properties of the coating. Moreover, the adhesion of water-based coatings can be enhanced by the functional shell powder (Shell powder/Mg(OH)₂@SA) filler through strong molecular forces between the aqueous fluorocarbon emulsion and the modified shell powder. The contact angle (CA) of the coating was approximately 150°, and the hydrophobic critical value of the coating was approximately 1550 times that of washing. Even after 1200 washes, the CA remained at 97°. This simple and environmentally friendly method was expected to enable the preparation of waterproof barriers with strong corrosion resistance on various substrates. The results demonstrated that the proposed filler is easy to store, simple to process, cost-effective in production, and environmentally friendly. Moreover, the coating utilizing the proposed filler exhibits excellent abrasion resistance, water resistance, adhesion, and thermal stability. This innovation provides an eco-friendly solution that repurposes discarded shells and mitigates environmental pollution. The recycling and reusing of discarded shells can significantly enhance the profitability of shellfish farming and contribute to sustainable development. Importantly, it will contribute to the mitigation of global warming and the achievement of carbon neutrality.